Organic Light-Emitting Diodes (OLEDs), due to their advantages of high contrast ratio, small thickness, wide angle of view, quick response, broad range of operating temperature, are applied more and more widely.
As shown in FIG. 1, an organic light-emitting diode display device includes an organic light-emitting diode display substrate 2. Each pixel unit of the organic light-emitting display substrate 2 is provided with an organic light-emitting diode comprising an anode 22, an organic light-emitting layer 23 and a cathode 24 which are sequentially arranged on a substrate 21. The anodes 22 of the organic light-emitting diodes are separated from one another and controlled by a thin film transistor array, and the organic light-emitting layer 23 and the cathode 24 of each organic light-emitting diode are integrally connected. The organic light-emitting layer 23 may include a Hole Injection Layer (HIL), a Hole Transfer Layer (HTL), an organic light-emitting material layer, an Electron Transfer Layer (ETL), an Electron Injection Layer (EIL) and other layer structure, and the cathode may be made from metal.
For a top emission type organic light-emitting diode display device, as its cathode 24 is required to be light-transmissive, the thickness of the cathode is relatively small so that the resistance thereof is relatively high. For this reason, an auxiliary electrode 25 may be provided on the substrate 21. The auxiliary electrode 25 may be in a latticed shape and is not electrically connected to the anode 22 or other structure. The cathode 24 may be connected to the latticed auxiliary electrode 25 through an auxiliary via hole 231 in the organic light-emitting layer 23, so that the resistance is reduced.
In fabricating the organic light-emitting diode display substrate 2 with the auxiliary electrode 25, in an existing method, a fine metal mask (FFM) plate is used in forming an organic light-emitting layer 23 by evaporation, so that an auxiliary via hole 231 is directly formed in the organic light-emitting layer 23 while forming the organic light-emitting layer 23 and the cathode 24 which is formed subsequently may be connected to the auxiliary electrode 25 through the auxiliary via hole 231.
The inventor has found at least the following problems in the prior art: the organic light-emitting layer of the organic light-emitting diode display substrate is of a multi-layer structure, and therefore multiple evaporations need to be performed; however, it can hardly ensure that the position of a fine metal mask plate is absolutely accurate during the multiple evaporations, so that the previously formed auxiliary via hole may be covered in the subsequent evaporation; in addition, for patterns having very high accuracy, the pattern of the fine metal mask plate is very small, and is likely to be blocked in the evaporation. In short, the existing method for forming the auxiliary via hole has high difficulty and low yield.